The present technology relates to an electrophoretic device including an electrophoretic particle and a porous layer, a display unit using the electrophoretic device, and an electronic unit using the display unit.
Lately, as various electronic devices such as mobile phones and personal digital assistants (PDA) become widely used, display units (displays) with low power consumption and high image quality have been increasingly demanded. Specially, in recent years, in association with birth of delivery business of electronic books, electronic book terminals for the purpose of reading textual information for a long time have attracted attentions. Therefore, displays having display quality suitable for such a reading purpose have been aspired.
As the display for reading, cholesteric liquid crystal displays, electrophoretic displays, electrochromic displays, twist ball displays, and the like have been proposed. Specially, displays categorized as reflective type displays are preferable. Since the reflective type displays perform light display by using reflection (scattering) of outside light as paper does, the reflective type displays provide display quality close to that of paper. Further, in the reflective type displays, a backlight is not necessitated, and therefore power consumption is able to be kept low.
A major candidate of the reflective type displays is the electrophoretic display that generates lighting (contrast) by using electrophoretic phenomenon, since power consumption is low and high-speed response is superior in the electrophoretic display. Therefore, various discussions have been made for display methods of the electrophoretic display.
Specifically, a method of dispersing two types of charged particles each having different optical reflection characteristics and different polarity in an insulating liquid, and moving the respective charged particles with the use of a polarity difference has been proposed (for example, see Japanese Examined Patent Application Publication No. 50-015115 and Japanese Patent No. 4188091). In this method, since distribution of the two types of charged particles is changed according to electric field, contrast is generated by using difference of the optical reflection characteristics.
Further, a method of dispersing charged particles in an insulating liquid, arranging a porous layer having optical reflection characteristics different from those of the charged particles, and moving the charged particles through the porous layer has been proposed (for example, see Japanese Unexamined Patent Application Publication No. 2005-107146, Japanese Examined Patent Application Publication No. 50-015120, Japanese Unexamined Patent Application Publication No. 2005-128143, and Japanese Unexamined Patent Application Publication No. 2002-244163). As the porous layer, a polymer film in which fine pores are formed by a boring process by using a laser, a woven cloth made of synthesized fibers or the like, an open-cell porous polymer, and the like are used. In this method, since distribution of the charged particles is changed according to the electric field, contrast is generated by using a difference of the optical reflection characteristics.
In addition, a method of encapsulating charged particles in a microcapsule and a method of sectioning a range where charged particles are able to exist in parts by a dividing wall structure have been proposed (for example, see Japanese Patent No. 2551783 and Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2003-526817). As a method of forming the dividing wall structure, an ultraviolet (UV) imprint method or the like has been proposed (for example, see Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2004-536336 and Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-509206). By these methods, aggregation, precipitation, convection, and the like of the charged particles are inhibited.